JPH03271513A - Valve system for four cycle engine - Google Patents

Abstract

PURPOSE:To improve engine output by arranging a first rocker arm between a second and a third rocker arms as well as fitting the second and third rocker arms into an eccentrically large diameter part formed on a rocker shaft so that the cam can be selected as the rocker shaft rotates. CONSTITUTION:A cam shaft 6 having middle/high speed cams 4, 5 on one side and on the other side of a low speed cam 3 is provided and a low speed rocker arm 7 and middle/high speed rocker arms 8, 9 are arranged at the bottom of each cam 3 - 5 with each rocker arm supported universally by a rocker shaft 11, respectively. The supporting portions of the middle/high speed rocker arms 8, 9 against the rocker shaft 11 are fitted into the rocker shaft 11 through eccentric bushes 12 and 13 which eccentrical diameters are larger than the diameter of the rocker shaft 11. A locational groove 32, a slide groove 33 and a slide holding groove 34 are engraved on the circumference of one end of the rocker shaft 11 in series and the tip of a stopper screw 36, which is screwed into the cylinder head, is fitted into each groove 32 - 34.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention is a four-stroke engine that can change the lift amount and opening timing of intake and exhaust valves according to the operating conditions. The present invention relates to a valve train, and particularly to a valve train for a four-stroke engine that can efficiently replace a shim installed at the head of a valve stem.

(Prior Art) Generally, in a four-stroke engine installed in a vehicle such as an automobile or a motorcycle, intake and exhaust valves are disposed above a combustion chamber, and these valves are driven by a valve train. That is, the valve train includes a camshaft that is linked to the crankshaft of the engine, and a cam formed on the camshaft moves the plate/exhaust valve up and down at a predetermined timing.

(Problem to be Solved by the Invention) By the way, the above-mentioned 4-cycle engine has the ability to obtain high output within a wide rotational speed range from low rotational speed to medium and high rotational speed, that is, has a wide power band. is desirable.

However, in conventional valve train systems, the valve opening/closing timing and lift amount are fixed, so output characteristics that only have a peak value in a specific engine speed range can be obtained, and therefore the output characteristics in the low engine speed range cannot be obtained. You are forced to choose whether to focus on the engine or the output characteristics in the medium and high rotation speed range.

This invention was made in consideration of the above-mentioned circumstances, and it is possible to improve the output within a wide rotation speed range, and also to efficiently replace the tappet clearance adjustment shim installed in the valve stem head. The purpose of the present invention is to provide a valve train for a four-stroke engine that can be used in a four-stroke engine.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes: a rocker shaft rotatably supported and formed with an eccentric large diameter portion; a first rocker arm directly fitted into the rocker shaft; second and third rocker arms disposed on both sides of the first rocker arm and fitted into the eccentric large diameter portion; and first, second and third rocker arms that drive the first, second and third rocker arms, respectively. 3 cams, the second and third cams are formed with the same cam profile, the cam profile of the first cam is formed differently from the cam profile, and the cams support the rocker shaft. A stopper screw is attached to the cylinder head, and the rocker shaft has a positioning groove for accommodating the tip of the stopper screw and regulating the rotational position of the rocker shaft, and a positioning groove for controlling the rotational position of the rocker shaft. The rocker shaft is characterized by being provided with a slide groove extending in the direction and allowing the rocker shaft to slide, and a slide holding groove continuous with the slide groove and holding the rocker shaft in the sliding position.

(Function) Therefore, according to the valve operating system for a four-stroke engine according to the present invention, by rotating the rocker shaft by a predetermined angle and rotating the eccentric large diameter portion, the cam floor surfaces of the second and 30th lever arms are rotated to the first position. 10 Change the position of the arm relative to the cam floor surface in the vertical direction.

When the cam floor surfaces of the first and 30th claw arms are moved downward relative to the cam floor surface of the 10th claw arm, the positions of the cam floor surfaces of the second and 30th claw arms and the second and third claw arms are changed downward.
The contact with the cam is released, the 10th lever arm contacts the first cam, and the valve of the 4-cycle engine
Driven by a cam.

Further, when the cam floor surfaces of the second and 30th lever arms are moved substantially upwardly or to the same position relative to the cam floor surface of the 10th lever arm, the contact between the 10th lever arm and the first cam is released, and the cam floor surface of the 10th lever arm is released. And the 30th hook arm and the second and third cams are in contact with each other, and the 4th
The valves of the cycle engine are actuated by the second and third cams. By rotating the rocker shaft and selecting a cam in this manner, engine output can be improved over a wide rotational speed range.

Furthermore, a slide holding groove is formed in the rocker shaft in succession to the slide groove, and the sliding position of the rocker shaft is maintained by receiving the tip of the stopper screw in the slide holding groove. Therefore, when sliding the rocker shaft and moving the first, second, and third rocker arms in order to replace the shim on the valve stem head, it is necessary for the operator to hold the slid rocker shaft by hand. Therefore, the shim replacement work becomes easier and the shim replacement efficiency can be improved.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

5 is a perspective view showing an embodiment of the valve train for a four-cycle engine according to the present invention, FIG. 2 is a partial plan view of a cylinder head to which the valve train shown in FIG. 5 is applied, and FIG. 3 and 3 are cross-sectional views taken along lines I-I and ■-■ in FIG. 2, respectively, and FIG. 6 is a plan view of the valve train shown in FIG. 5.
7 and 8 are operating state diagrams showing the operation of the valve train of FIG. 5.

This valve train is disposed on the intake side and the exhaust side of one cylinder of the engine, respectively. Therefore, the fifth
The valves 1 and 2 shown in FIGS. 8 and 3 are arranged for intake or exhaust.

This embodiment includes a low-speed cam 3 as a first cam, a medium-high speed cam 4 as a second cam, and a third cam disposed on one side and the other side of the low-speed cam 3, respectively. A camshaft 6 (FIG. 5, FIG. 6, FIG. 2) also has a cam 5 for medium and high speeds, and cams 3.4 and 5.
A rocker arm 7 for low speeds as a 10th lever arm, a rocker arm 8 for medium and high speeds as a 20th lever arm, and a rocker arm 9 for medium and high speeds as a 30th lever arm, and these rocker arms 7.8 and 9. The rocker shaft 11 is fitted with support parts 7a, 8a, and 9a, and is rotatably supported by a rocker arm bearing part 30 (FIGS. 1 and 2), which will be described later.

The tip of the low-speed rocker arm 7 branches into two directions, and both branched ends 7b abut the stem heads of the valves 1 and 2, which open and close the combustion chamber 27 (FIG. 3) of the engine, respectively. In addition, the support portion 7a of the low-speed rocker arm 7
is directly fitted onto the rocker shaft 11 and is rotatably provided.

The support portion 8a of the medium/high speed rocker arm 8 is rotatably fitted onto the rocker shaft 11 via an eccentric bushing 12 having a larger diameter than the rocker shaft 11. As shown in FIG. 7, this eccentric bushing 12 has an axis eccentric from the center of the rocker shaft 11, and is detachably fixed to the rocker shaft 11 by a retaining pin 10. Therefore, this eccentric bushing 12 functions as an eccentric large diameter portion of the rocker shaft 11.

As shown in FIG. 6, the support portion 9a of the medium/high speed rocker shaft 9 also rotates relative to the rocker shaft 11 via an eccentric bush 13 that has the same shape as the eccentric bush 12 and is eccentric in the same direction. Possibly inserted. This eccentric bushing 13 is also attached to the rocker shaft 11 by the retaining pin 10.
It is removably fixed to the shaft and functions as an eccentric large diameter section.

In addition, each tip portion 8b of the rocker arms 8 and 9 for medium and high speeds is
The lower surfaces of 9b and 9b are in contact with one and the other branch tip portions 7b of the low-speed rocker arm 7 via shims 14a, respectively. Branch portion 7 of these low-speed rocker arms 7
The contact points between the tip portions 8b and 9b of the middle and high speed rocker arms 8 and 9 are set approximately on the axes of the valves 1 and 2.

Therefore, as shown in FIGS. 3 and 7, when the low-speed cam 3 pushes down the cam floor surface 7C of the low-speed rocker arm 7 and lowers each tip 7b of the low-speed rocker arm 7, each tip of the rocker arms 8 and 9 Portions 8b and 9b descend following this branching portion 7b due to gravity. On the other hand, when the medium-high speed cams 4 and 5 push down the cam floor surfaces 8C and 9C of the medium-high speed rocker arms 8 and 9, as shown in FIG.
Since the distal ends 8b and 9b of the low speed rocker arm 7 press down on the distal end portions 7b of the low speed rocker arm 7, the distal end portions 7b are forcibly lowered.

The shim 14a is a T-shaped shim in longitudinal section, and is fitted into the dividing portions 7b of the low-speed rocker arm 7 from above. Further, a capped cylindrical shim 14b is crowned on the valve stem heads of the valves 1 and 2, and this shim 14b
The lower surface of the tip 7b of the low-speed rocker arm 7 comes into contact with this. These shims 14a and 14b are used for adjusting the tappet clearance of the valves 1 and 2.

Also, among the cams 3.4 and 5, the medium-high speed cam 4
and 5 have the same cam profile, and the low speed cam 3 has a different cam profile from the cam profile of these medium and high speed cams 4 and 5. In other words,
The cam profile of the low-speed cam 3 is set so that an appropriate valve lift amount and valve opening/closing timing can be obtained when the engine is operated in a low rotational speed range. Also,
The cam profiles of the medium and high speed cams 4 and 5 are set so as to obtain a valve lift amount and valve opening/closing timing suitable for when the engine is operated in a medium and high speed range.

The above-mentioned valve lift amount is the stroke length of valves 1 and 2, and coincides with the cam lift amount. In Fig. 9, the cam profile of the low-speed cam 3 is shown as a solid line A (cam lift amount 1
a'), and the cam profiles of the medium and high speed cams 4 and 5 are shown by a broken line B (cam lift amount Ab).

As is clear from FIG. 9, the cam profiles of the medium and high speed cams 4 and 5 are set so that a larger valve lift amount can be obtained than that of the low speed cam 3.

The two-dot chain line C in FIG. 9 indicates the state when the rocker shaft 11 is rotated to position the thick tops 12a and 13a of the eccentric bushes 12 and 13 diagonally forward (FIGS. 3 and 7). The cam profiles of cams 4 and 5 for medium and high speeds are shown.

By the way, as shown in FIGS. 1, 2, and 5,
The rocker shaft 11 is rotated by a hydraulic cylinder 15 operated by oil pressure from the engine. A rack 16 is attached to the piston (not shown) of this hydraulic cylinder 15.
The rack 16 is engaged with a pinion 17 formed at one end of the rocker shaft 11. These hydraulic cylinder 15, rack 16 and pinion 17
constitutes the drive mechanism. In addition, the hydraulic cylinder 15 includes
A low-speed hydraulic boat 18 and a high-speed hydraulic boat 19 are provided, and hydraulic pressure from the engine is selectively guided to each boat 18,19.

When the engine speed is in the low speed range, hydraulic pressure is supplied to the low speed hydraulic boat 18, the rack 16 is pulled back, the pinion 17 is rotated in the direction of arrow 0, and the eccentric bushes 12 and 13 are rotated as shown in FIG. As shown in FIG. 7, the thick top portions 12a and 13a are rotated so as to be positioned diagonally forward. Further, when the engine speed is in the medium/high speed range, hydraulic pressure is supplied to the medium/high speed hydraulic boat 19, the rack 16 is pushed out, the pinion 17 is rotated in the direction of arrow P, and the eccentric bush 12 and 13 is rotated so that its thick top portions 12a and 13a are positioned diagonally rearward, as shown in FIG.

In this way, the rocker shaft 11 is connected to the hydraulic cylinder etc.
5, 16.17, the eccentric bushing 12.13
The thick top parts 12a and 13a of the rocker shaft 1 are always connected to the rocker shaft 1.
It is configured to rotate in the range from diagonally forward to diagonally backward on the upper half side of 1.

Rocker shaft 11 and hydraulic cylinder 1 as described above
5 etc. are arranged in the cylinder head 21 shown in FIGS. 1 to 3. The rocker shaft 11 is connected to the cylinder head 21
There are four in total, one at the front and rear of the vehicle, and one at the left and right sides of the vehicle, extending in the left-right direction of the vehicle. Each rocker shaft 11 is rotatably supported by a rocker shaft bearing 30. A lower half bearing hole 22 for supporting the camshaft 6 is formed above these rocker shafts 11 .

Also, a valve guide 23 (
(FIGS. 2 and 3) are arranged, and stud bolt insertion holes 24 are formed. Further, a mating surface 25 with the head cover is formed at the upper part of the cylinder head 21, and a cam chain chamber 26 is formed at the center position of the cylinder head 21 in the left-right direction of the vehicle. A hydraulic cylinder 15 and a rack 16 are arranged within this cam chain chamber 26.

Further, as shown in FIG. 3, a combustion chamber 27 is formed in the lower part of the cylinder head 21, and an intake boat 28 and an exhaust boat 29 are formed in communication with this combustion chamber 27. The valve faces of valves 1 and 2 are arranged at the boundary between combustion chamber 27 and intake boat 28 and exhaust boat 29. Valve spring 20 and low speed rocker arm 7,
The action of the medium and high speed rocker arms 8 and 9 opens and closes the intake boat 28 and the exhaust boat 29.

Two sets of the low-speed rocker arm 7 and the medium-high speed rocker arms 8 and 9 are installed on one rocker shaft 11, as shown in FIG. Each set of low-speed rocker arm 7
The positions of the medium and high speed rocker arms 8 and 9 are regulated together with the rocker shaft 11 by a positioning spring 31 interposed in the rocker shaft 11.

That is, the low-speed rocker arm 7, the medium-high speed rocker arms 8 and 9, and the rocker shaft 11 are pressed toward the center of the cylinder head 21 by the biasing force of the positioning spring 31.

Furthermore, as shown in FIGS. 1 and 4, positioning grooves 32, slide grooves 33, and slide retaining grooves 34 are continuously carved on the outer layer of the other end of the rocker shaft 11, in which the pinion 17 is formed at one end. will be established. The positioning groove 32 is formed along the circumferential direction of the rocker shaft 11 over the range of the rotation angle of the rocker shaft 11. Furthermore, the slide groove 33 extends in the axial direction of the rocker shaft 11 from one or both ends of the positioning groove 32 . In Figure 4,
A case is shown in which the slide groove 33 extends from one end. Furthermore, the slide retaining groove 34 is formed to extend a certain amount from the slide groove 33 in the circumferential direction of the rocker shaft 11.

On the other hand, a screw hole 35 is formed in the cylinder head 21 at a position corresponding to the positioning groove 32, and a stopper screw 36 is screwed into this screw hole 35.

The tip of this stopper screw 36 is the positioning groove 32,
It is provided so that it can be accommodated in the slide groove 33 and the slide holding groove 34.

When the rocker shaft 11 rotates due to the operation of the hydraulic cylinder 15, the tip of the stopper screw 30 comes into contact with both ends of the positioning groove 32, thereby regulating the rotational position of the rocker shaft 11.

Moreover, the slide groove 33 and the slide holding groove 34 function when replacing the shims 14b installed at the stem heads of the valves 1 and 2 and adjusting the tappet clearance. That is, when replacing the shim 14b, the rocker shaft 11 is slid to the outside of the cylinder head 21 against the urging force of the positioning spring 31, and the low-speed rocker arm 7 and the medium-high speed rocker arms 8 and 9 are moved in the same direction. need to be moved. At this time, the tip of the stopper screw 36 moves within the slide groove 33, and therefore, the slide groove 33 allows the rocker shaft 11 to slide. Thereafter, by rotating the rocker shaft 11 by a certain amount, the tip of the stopper screw 36 moves within the slide holding groove 34. As a result, the slide holding groove 34 can maintain the sliding position of the rocker shaft 11 by engaging with the stopper screw 36.

In FIG. 1, reference numeral 37 is a bearing housing for the camshaft 6, and reference numeral 38 is a camshaft housing.

Next, the effects will be explained.

When the engine is in the low rotation speed range, the hydraulic cylinder 15
When the rocker shaft 11 rotates in the direction of arrow O in FIG. 5 due to the operation of , the thick tops 12a and 13a of the eccentric bushes 12 and 13 are located diagonally forward (FIGS. 3 and 7). As a result, the cam floor surfaces 8C and 9C of the medium and high speed rocker arms 8 and 9 move downward relative to the cam floor surface 7c of the low speed rocker arm 7. Therefore, gaps are formed between the circumferential surfaces of the medium and high speed cams 4 and 5 and the cam floor surfaces 8c and 9c of the medium and high speed rocker arms 8 and 9,
As a result, the medium and high speed cams 4 and 5 idle.

Also, at this time, the low-speed rocker arm 7 is constantly pushed upward centering on the narrow center of the rocker shaft 11 by the urging force of the valve spring 20, so that its cam floor surface 7c comes into contact with the circumferential surface of the low-speed cam 3. . Therefore, when the camshaft 6 rotates, the valves 1 and 2 move up and down based on the lift characteristic A of the low-speed cam 3 shown in FIG. In other words, valves 1 and 2 open and close the combustion chamber while ensuring a valve lift amount suitable for a low engine speed range.

On the other hand, when the rocker shaft 11 rotates in the direction of arrow P in FIG.
Thick-walled top portions 12a and 1.3a, respectively, are located diagonally rearward (FIG. 8).

As a result, the cam floor surfaces 8c and 9c of the rocker arms 8 and 9 for medium and high speeds move to the road force or the same position relative to the cam floor surface 7C of the rocker arm 7 for low speeds, and these cam floor surfaces 8C and 9C respectively contact with the circumferential surfaces of the cams 4 and 5.

Here, as shown in FIG. 9, the medium and high speed cams 4 and 5 are formed to have a larger cam lift than the low speed cam 3, so the camshaft 6 is rotated under the conditions shown in FIG. In this case, the low-speed cam 3 idles, while the medium-high speed cams 4 and 5 operate the valve 1 via the medium-high speed rocker arms 8 and 9, respectively, based on the lift characteristic B shown in FIG.
and 2. As a result, valves 1 and 2 are
Opens and closes the combustion chamber while ensuring a valve lift suitable for the engine's medium and high speed range.

By the way, when the rocker shaft 11 is rotated by the action of the hydraulic cylinder 15, rack 16, and pinion 17, the stopper screw 36 comes into contact with each end of the positioning groove 32. As a result, the rocker shaft 11 has the above-mentioned thick top portions 12a of the eccentric bushes 12 and 13.
and 1id (FIG. 7) where the thick top portions 12a and 13a are diagonally forward (FIG. 8).

According to the above embodiment, the low speed cam 3 has a cam profile suitable for the low engine speed range, and the medium and high speed cams 4 and 5 have cam profiles suitable for the medium and high engine speed range. Furthermore, the rocker arm 8 for medium and high speeds is attached to the eccentric bushes 12 and 13 of the rocker shaft 11.
and 9 are rotatably inserted into each other, and the low-speed rocker arm 7 is directly inserted into the rocker shaft 11. As the rocker shaft 11 rotates, the low-speed cam 3 and the low-speed rocker arm 7 are brought into contact with each other, and the low-speed rocker arm 7 is inserted into the rocker shaft 11. Since the contact between the cams 4 and 5 and the medium-high speed rocker arms 8 and 9 can be selected, the valves 1 and 2 can be selectively driven by the low-speed cam 3 or the medium-high speed cam 4.5. .

Therefore, the output of the four-stroke engine can be improved over a wide engine speed range from low engine speeds to medium and high engine speeds.

Also, since the selection of the low speed cam 3 and the medium and high speed cams 4 and 5 is performed by rotating the eccentric bushings 12 and 13, the cam 3. 4. No large stress is generated in each part when selecting item 5. For this reason, cam 3. 4.
5 can be selected smoothly.

Furthermore, when replacing the shim 14b to adjust the tappet clearance with the camshaft 6 assembled, the rocker shaft 11 must be slid outward of the cylinder head 21 against the biasing force of the positioning spring 36. After that, rotate it slightly in the circumferential direction. Then, the tip of the stopper screw 36 moves inside the slide groove 33 and then reaches inside the slide holding groove 34. Due to the engagement between the stopper screw 36 and the slide holding groove 34, the rocker shaft 11 is stopped at that position and is held in a state where it slides outward of the cylinder head 21. In this state, the low-speed rocker arm 7 and the medium-high speed rocker arms 8 and 9 slide, and since these rocker arms 7.8 and 9 do not exist directly above the shim 14b, the shim 14
b can be easily replaced.

In this way, the rocker shaft 11 can be held in the sliding position when replacing the shim 14b, so the operator can hold the shim 1 with both hands.
4b can be replaced. This makes replacement work easier,
Since it can be done in a short time, the shim 14b can be replaced efficiently.

In the above embodiment, the cam profiles of the medium and high speed cams 4 and 5 are shown in broken line B in FIG. 9, but the cam profiles of the medium and high speed cams 4 and 5 are shown in FIG. The lifts of the valves 1 and 2 at medium and high speeds of the engine may be changed as shown by the broken line B' in FIG. 1 or the broken line B' in FIG.

Further, in the above embodiment, a case has been described in which the hydraulic cylinder 15 is used as a rotational drive source for the rocker shaft 11, but a motor is used as the rotational drive source, and the rocker shaft 11 is rotationally driven by a power transmission means such as a pulley and a belt. You may also do so.

〔Effect of the invention〕

As described above, according to the valve train for a four-cycle engine according to the present invention, the eccentric large diameter portion is formed in the rotatably supported rocker shaft, and the second and third
Since the 0th lever arm was fitted into this eccentric large diameter portion, and the 10th lever arm was placed between the 2nd and 30th lever arms and directly fitted into the rocker shaft, the rotation of the cam due to the rotation of the rocker shaft was Depending on the selection, engine output can be improved over a wide rotational speed range.

In addition, the rocker shaft is continuously formed with a positioning groove, a slide groove, and a slide holding groove, and the tip of the stopper screw is accommodated in these grooves, so when replacing the shim for tappet clearance adjustment, the rocker When sliding the shaft, the rocker shaft can be held in the sliding position by engaging the tip of the stopper screw with the slide holding groove, making shim replacement easier and improving shim replacement efficiency. be able to.

[Brief explanation of drawings]

Figure 1 is a sectional view taken along the line I-I in Figure 2, and Figure 2 is a cross-sectional view of the
FIG. 3 is a sectional view taken along line mm in FIG. 2, and FIG. 4 is a perspective view showing the other end of the rocker shaft in FIG. 1. 5 is a perspective view showing an embodiment of the valve train for a four-cycle engine according to the present invention, and FIG. 6 is a plan view of the valve train shown in FIG.
7 and 8 are operating state diagrams showing the action of the valve train in FIG. 5, FIG. 9 is a diagram showing the cam profile of the cam in FIGS. 1 and 5, and FIGS. 10 and 11. 9A and 9B are diagrams showing respective modifications of the cam profile shown in FIG. 9. FIG. 1.2...Valve, 3...Low speed cam, 4,5...
・Medium/high speed cam, 7...Low speed rocker arm, 8, 9
... Rocker arm for medium and high speeds, 11 ... Rocker shaft, 12.13 ... Eccentric bush, 14b ... Shim, 1 ... Cylinder head, 31 ... Positioning spring, 32 ... Positioning groove , 33... slide groove,
34... Slide holding groove, 36... Stopper screw, A... Cam profile of low speed cam, B...
Cam profile for medium and high speed cams. Camshaft rotation angle Figure 9 Camshaft rotation angle Figure 10 Camshaft rotation angle Figure 11 Procedure amendment (voluntary) May 31, 1990

Claims (1)

[Claims] a rocker shaft rotatably supported and formed with an eccentric large diameter portion; a first rocker arm directly fitted into the rocker shaft; and first, second and third cams that drive the first, second and third rocker arms, respectively. A third cam is formed to have the same cam profile, a cam profile of the first cam is formed different from the cam profile, and a stopper screw is attached to a cylinder head supporting the rocker shaft, and a stopper screw is attached to the cylinder head supporting the rocker shaft. The shaft includes a positioning groove for accommodating the tip of the stopper screw and regulating the rotational position of the rocker shaft, and a slide groove extending from the positioning groove in the axial direction of the rocker shaft to allow the rocker shaft to slide. and a slide holding groove that is continuous with the slide groove and holds the slide position of the rocker shaft.